MIPS: Avoid HeapObject check in HStoreNamedField.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 562c88d34d23b6c12840494c159461319a2e0949..30fe8c4c8bdac13cefb46aa97225d6d8891a9687 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -2267,13 +2267,7 @@ LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   // We need a temporary register for write barrier of the map field.
   LOperand* temp = needs_write_barrier_for_map ? TempRegister() : NULL;
 
-  LInstruction* result = new(zone()) LStoreNamedField(obj, val, temp);
-  if (!instr->access().IsExternalMemory() &&
-      instr->field_representation().IsHeapObject() &&
-      !instr->value()->type().IsHeapObject()) {
-    result = AssignEnvironment(result);
-  }
-  return result;
+  return new(zone()) LStoreNamedField(obj, val, temp);
 }